Received:06 December 2025;Accepted:25 February 2026;Published:30 March 2026 ABSTRACT:In the last decade,the importance of sustainable construction and artificial intelligence(AI)in civil engineering has been underline...Received:06 December 2025;Accepted:25 February 2026;Published:30 March 2026 ABSTRACT:In the last decade,the importance of sustainable construction and artificial intelligence(AI)in civil engineering has been underlined in many studies.Numerous studies highlighted the superiority of AI techniques over simple and mathematical regression analyses,which suffer from relatively poor generalization and an inability to capture highly non-linear relationships among inputs and output(s)parameters.In this study,to evaluate the compressive strength of concrete with glass powder(GP)and recycled aggregates,600 concrete samples were tested in the laboratory,and their results were evaluated.For intelligent assessment of concrete compressive strength(CCS),the study utilized an improved artificial neural network(ANN)with particle swarm optimization(PSO)algorithm and imperialist competitive algorithm(ICA).For training the models,the experimentally obtained data were used.The concrete ingredients formed the inputs of the AI-based predictive models of CCS.The experimental findings reveal that the implementation of recycled coarse aggregates in concrete from a sustainable construction point of view is advantageous and can enhance the CCS by 11.43%.Apart from that,findings indicate that utilization of 10%GP can lead to a nearly 20%increase in CCS(from 44.6 to 54.1 MPa).Additionally,the experimental observations show almost 40%improvement of CCS when 5%micro silica was used in the concrete mixture.Based on the findings,the study suggests the utilization of waste glass powder to partially replace cement in concrete,which can reduce the amount of cement production.This reduction from economic,energy-saving,and environmental(reduction in greenhouse gas emissions)points of view is of interest.On the other hand,the AI results show that the PSO-based ANN model outperforms the ICA-based ANN for the utilized dataset.According to the findings,the PSO-based ANN predictive model(with a coefficient of determination value of 0.939 and root mean square value of 0.113 for testing data)is a capable tool in predicting the CCS.Hence,this study recommends the implementation of AI-based models in CCS assessment.展开更多
We investigated the effects of fly ash(FA)content on the mechanical properties of recycled aggregate concrete(RAC)and its regeneration potential under freeze and thaw(F-T)cycles.The physical properties of second-gener...We investigated the effects of fly ash(FA)content on the mechanical properties of recycled aggregate concrete(RAC)and its regeneration potential under freeze and thaw(F-T)cycles.The physical properties of second-generation recycled concrete aggregates(RCA)were used to analyze the regeneration potential of RAC after F-T cycles.Scanning electron microscopy was used to study the interfacial transition zone microstructure of RAC after F-T cycles.Results showed that adding 20%FA to RAC significantly enhanced its mechanical properties and frost resistance.Before the F-T cycles,the compressive strength of RAC with 20%FA reached 48.3 MPa,exceeding research strength target of 40 MPa.A majority of second-generation RCA with FA had been verified to attain class Ⅲ,which enabled their practical application in non-structural projects such as backfill trenches and road pavement.However,the second-generation RCA with 20%FA can achieve class Ⅱ,making it ideal for 40 MPa structural concrete.展开更多
A comprehensive full-sieve-hole grading correction method was used to adjust aggregate gradings.The fatigue properties of recycled concrete aggregate(RCA)asphalt mixtures were investigated using an improved indirect t...A comprehensive full-sieve-hole grading correction method was used to adjust aggregate gradings.The fatigue properties of recycled concrete aggregate(RCA)asphalt mixtures were investigated using an improved indirect tensile fatigue test under temperature-humidity coupling based on 20-year meteorological data of Beijing,and the degeneration mechanism was further explored by scanning electron microscopy and energy-dispersive spectroscopy.The experimental results indicate that replacing 5-20 mm coarse limestone aggregate(LA)with RCA at a 50% substitution volume can mitigate the impact of RCA variations on the asphalt mixture proportioning design.All RCA asphalt mixtures have lower initial fatigue properties than the LA asphalt mixture.However,under temperature-humidity coupling,the long-term fatigue property of an RCA asphalt mixture with a low proportion of recycled brick exceeds that of the LA asphalt mixture,and the fatigue life decline rate of the RCA asphalt mixture during 10-year service decreases by approximately 25%.This is due to the penetration of the asphalt mortar into the RCA through the pores and cracks on the RCA surface.It forms an interfacial transition zone composed of asphalt mortar and cement mortar and further reduces the mixture damage caused by the water and freeze-thaw conditions.展开更多
Crushing waste coral concrete into recycled aggregates to create recycled coral aggregate concrete(RCAC)contributes to sustainable construction development on offshore islands and reefs.To investigate the impact of re...Crushing waste coral concrete into recycled aggregates to create recycled coral aggregate concrete(RCAC)contributes to sustainable construction development on offshore islands and reefs.To investigate the impact of recycled coral aggregate on concrete properties,this study performed a comprehensive analysis of the physical properties of recycled coral aggregate and the basic mechanical properties and microstructure of RCAC.The test results indicate that,compared to coral debris,the crushing index of recycled coral aggregate was reduced by 9.4%,while porosity decreased by 33.5%.Furthermore,RCAC retained the early strength characteristics of coral concrete,with compressive strength and flexural strength exhibiting a notable increase as the water-cement ratio decreased.Under identical conditions,the compressive strength and flexural strength of RCAC were 12.7% and 2.5% higher than coral concrete's,respectively,with porosity correspondingly reduced from 3.13% to 5.11%.This enhancement could be attributed to the new mortar filling the recycled coral aggregate.Scanning electron microscopy(SEM)analysis revealed three distinct interface transition zones within RCAC,with the‘new mortar-old mortar’interface identified as the weakest.The above findings provided a reference for the sustainable use of coral concrete in constructing offshore islands.展开更多
Egypt has a high attitude in construction and demolition waste (CDW) amounts causing a negative impact on the environment. The use of such waste for infrastructures applications can be useful for each environment and ...Egypt has a high attitude in construction and demolition waste (CDW) amounts causing a negative impact on the environment. The use of such waste for infrastructures applications can be useful for each environment and in addition an economic benefit to it in the construction. This study explores the possibility of replacing natural coarse aggregate with recycled concrete construction and demolition waste aggregate for general purpose concrete (i.e. plain concrete and low strength structural concrete). Different samples of CDW were extracted from different demolition sites and landfill locations around Tanta city area for the experimental investigation. CDW was crushed with all its hard constituents (e.g. concrete, brick etc.) found in the landfill. Coarse size crushed CDW was used as a coarse aggregate for concrete. Main characteristics of CDW aggregate determined in addition to the main properties of concrete which was made using this aggregate were measured. The results showed that the CDW could be transformed into recycled concrete aggregate leading to reduction in the concrete compressive strength ranged from 37% to 62% depending on the type of the CDW constituents.展开更多
Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may ...Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.展开更多
In order to study the effects of the contents of used mortar recycled aggregate(OMRA)and brick recycled aggregate(BRA)on the deformation properties of recycled aggregate concrete(RAC),under uniaxial compression condit...In order to study the effects of the contents of used mortar recycled aggregate(OMRA)and brick recycled aggregate(BRA)on the deformation properties of recycled aggregate concrete(RAC),under uniaxial compression conditions,The RAC of OMRA(0%,5%,10%,and 15%)and BRA(0%,3%,6%,9%,12%,and 15%)were studied.The experimental results show that,under uniaxial compression,the interfacial relationships of RAC containing OMRA and BRA between different materials are more complex,and the failure mechanism is also more complex.The content of OMRA and BRA had significant influence on the deformation behavior of RAC.When the content of OMRA and BRA is high,it is difficult for existing formulas and models to accurately represent the actual value.In this study,the influence of OMRA and BRA content is taken into account,and the existing formulas for calculating concrete deformation are modified,so that these formulas can more accurately calculate the elastic modulus,peak strain and ultimate strain of recycled concrete.The stress-strain formula of Guo concrete fits the stress-strain curve of concrete very well.We modified the formula on the basis of Guo formula to make the formula more suitable for the stress-strain curve of recycled concrete containing old mortar and brick,and the theoretical model proposed has better fitting accuracy.The study provides a valuable reference for nonlinear analysis of recycled aggregate concrete structures under different proportions of OMRA and BRA.展开更多
Exploring alternative aggregates or recycled aggregates to substitute traditional concrete aggregates,particularly sand aggregates,which are becoming more limited and must comply with environmental protection standard...Exploring alternative aggregates or recycled aggregates to substitute traditional concrete aggregates,particularly sand aggregates,which are becoming more limited and must comply with environmental protection standards,is essential.Research has explored various alternative materials to sand in concrete,including concrete from demolished buildings,and broken glass from projects,among others.Investigating the use of recycled broken glass to substitute sand aggregates and implementing this research in compression columns is crucial.This paper examines the compressive behavior of reinforced concrete columns that utilize recycled glass particles as a substitute for sand in concrete.The research findings establish the relationships:load and vertical displacement,load and deformation at the column head,mid-column,and column base;the formation and propagation of cracks in the column,while considering factors such as the percentage of recycled glass,the arrangement of stirrups,and the amount of load-bearing steel influencing the performance of square reinforced concrete columns under compression.The feasibility of using recycled glass as a substitute for sand in column structures subjected to compression has been demonstrated,with the ideal replacement content for sand aggregate in reinforced concrete columns in this study ranging from 0%to 10%.The column’s load-bearing ability dropped from 250 kN to 150 kN when 100%recycled glass was used instead of sand.This is a 40%drop,and cracks started to show up sooner.The research will support recycling broken glass instead of using sand in building,improving the environment and reducing natural sand use.展开更多
In order to realize the resource utilization of construction waste,industrial waste slag and silt,this paper used Portland cement,mineral waste residue and phosphogypsum composite to make cementing material(CMPS)with ...In order to realize the resource utilization of construction waste,industrial waste slag and silt,this paper used Portland cement,mineral waste residue and phosphogypsum composite to make cementing material(CMPS)with construction waste recycled aggregate to solidify silt.The mechanical properties of the solidified silt were analyzed by laboratory solidification test and microscopic examination respectively.In order to clarify the mineral composition,microscopic morphology and pore characteristics of the regenerated aggregate and CMPS solidified silt,X-ray diffractometer(XRD),scanning electron microscope(SEM),and nitrogen adsorption pore analyzer(NA)were used to further explore and analyze the regenerated aggregate and CMPS solidified silt effectively,and further reveal the internal mechanism of the regenerated aggregate and CMPS solidified silt effectively.The experimental results show that the strength of Portland cement-mineral waste residue phosphogypsum terpolymer system curing agent increases by 107.34%than that of single Port-land cement solidified silt at 56 d,and the strength of CMPS solidified silt increases by 25.68%under the action of recycled aggregate framework.The curing age and moisture content of the silt have a high correlation with the strength of the solidified silt.Therefore,the influence law of the above two influencing factors on its mechanical properties is further explored and the strength prediction is made.The microscopic test results show that,based on the hydration of Port-land cement and the pozzolans reaction of mineral waste residue,the solidified system has produced calcium silicate hydrate gel and ettringite crystals with gelatinous properties,which helps to fill the pores and form a denser structure.展开更多
Accurately predicting the compressive strength of recycled aggregate concrete(RAC)incorporating supplementary cementitious materials(SCMs)remains a critical challenge due to the heterogeneous nature of recycled aggreg...Accurately predicting the compressive strength of recycled aggregate concrete(RAC)incorporating supplementary cementitious materials(SCMs)remains a critical challenge due to the heterogeneous nature of recycled aggregates(RA)and the complex interactions among multiple binder constituents.This study advances the field by developing the most extensive and rigorously preprocessed database to date,which comprises 1243 RAC mixtures containing silica fume,fly ash,and ground-granulated blast-furnace slag.A hybrid,domain-informed machine-learning framework was then proposed,coupling optimized Extreme Gradient Boosting(XGBost)with civil engineering expertise to capture the complex chemical and microstructural mechanisms that govern RAC performance.Systematic grid-search optimization(n_estimators=50,learning_rate=0.2,max_depth=7)produced superior predictive accuracy(training R^(2)=0.9923,testing R^(2)=0.937;MAE=2.378 MPa;RMSE=3.591 MPa),which outperformed Extra Trees,Light Gradient Boosting,and traditional regressors.Beyond prediction,model interpretability was achieved using Shapley additive explanations and partial dependence analyses,which revealed curing age as the dominant strength driver,while water-to-binder ratio and recycled aggregate water absorption exhibited strong negative influences.Three-dimensional interaction plots further demonstrated how optimal superplasticizer dosages reduce the strength loss associated with high recycled aggregate content.In summary,this work provides a novel,explainable,and data-driven framework that achieves high predictive accuracy with mechanistic transparency and offers a powerful,interpretable tool for the design and optimization of sustainable RAC mixtures.展开更多
To examine the influences of waste polypropylene fiber(PPF)on the strength and internal pore structure of recycled aggregate concrete incorporating iron ore tailings,both the cubic compressive strength and axial compr...To examine the influences of waste polypropylene fiber(PPF)on the strength and internal pore structure of recycled aggregate concrete incorporating iron ore tailings,both the cubic compressive strength and axial compressive strength of the concrete were measured.Additionally,the microstructure was analyzed using scanning electron microscopy.The evolution of pore structure parameters,including pore size distribution,pore type distribution,and nuclear magnetic resonance spectral area in the concrete,was investigated through nuclear magnetic resonance(NMR)analysis.A model correlating the concrete's pore structure with its macroscopic performance was subsequently developed based on fractal theory.The results demonstrate that an appropriate amount of PPF created a bridging effect that decelerated the progression of macro cracks,enhanced the ductility of the concrete's failure mode,and increased both cubic compressive strength and axial compressive strength,with the most effective dosage being approximately 0.6%.An appropriate amount of PPF(ranging from 0.3%to 0.6%)facilitated the formation of harmless pores and shifted the pore size distribution towards medium and small sizes.Specifically,a fiber content of 0.6%resulted in the most significant reduction in the T2 spectral area.Furthermore,the pore structure of concrete exhibits distinct fractal characteristics.As the PPF content increased,the fractal dimension initially rose and then declined,demonstrating a strong correlation with the mechanical properties.展开更多
The degradation performance of pervious concrete containing TiO_(2)/LDHs-loaded recycled aggregates for NO gas was analyzed using a gas phase catalytic degradation test device,simulating different environmental condit...The degradation performance of pervious concrete containing TiO_(2)/LDHs-loaded recycled aggregates for NO gas was analyzed using a gas phase catalytic degradation test device,simulating different environmental conditions such as load,ambient temperature,and illumination intensity,which provides theoretical support for practical engineering.The experimental results indicate that when the ambient temperature is controlled at 25℃and the illumination intensity is 30 W/m^(2),the sample prepared by soaking recycled aggregates in a 0.8%TiO_(2)/LDHs suspension exhibits the highest photocatalytic degradation rate for NO gas,reaching 72.54%.Further investigation on the influence of environmental temperature reveals that,at 25℃,the maximum photocatalytic degradation rate for NO gas is 72.9%.Moreover,at an illumination intensity of 40 W/m^(2),the maximum photocatalytic degradation rate for NO gas is 87.08%.Additionally,after three repeated photocatalytic tests,the sample demonstrates good stability,with a photocatalytic degradation rate of 58%.The nitrogen content in the eluent obtained from soaking the sample was determined to be 0.0022 mol/L,with a recovery rate of 80%.The adsorption experiment demonstrates that the sample exhibits a favorable adsorption effect on nitrate ions,reaching a maximum of 56.8%.展开更多
The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully rep...The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully replace natural fine aggregates was investigated.The results indicated that a 50% FA content significantly increased the compressive strength of RFA-HDCC by 13.93%.However,a?further increase in FA content led to a drastic decrease.The increased fly ash content substantially reduced the flexural and tensile strength;however,it markedly increased the matrix strain capacity,resulting in a 53.73% increase in the peak strain when FA was raised to 70%.Regarding durability,the increase in FA content negatively affected the chloride ion permeability and carbonation resistance.However,the increase in FA content initially improved the frost resistance of RFA-HDCC,peaking at 50% FA and deteriorating at 60% and 70% FA content.展开更多
This study meticulously examined the compaction and sulfate erosion resistance of cement-stabilized materials incorporating recycled brick-concrete aggregate (RBCA).To explore the effects of recycled brick aggregate (...This study meticulously examined the compaction and sulfate erosion resistance of cement-stabilized materials incorporating recycled brick-concrete aggregate (RBCA).To explore the effects of recycled brick aggregate (RBA) with varying particle sizes,three size ranges (4.75-9.5 mm,9.5-19 mm and 19-31.5 mm) were used to replace 20% of the corresponding particle sizes of recycled concrete aggregate (RCA) in cement-stabilized materials.The findings indicated that cement-stabilized materials utilizing RBA and RCA exhibited a lower maximum dry density and a higher optimum moisture content than natural aggregate cement-stabilized materials.The use of RBA with a particle size of 4.75-9.5 mm resulted in a lower maximum dry density and a higher optimum moisture content than 9.5-19 mm and 19-31.5 mm.Furthermore,the 7-day unconfined compressive strength of RBCA cement-stabilized materials with RBA of 4.75-9.5 mm demonstrated superior results compared to those with larger particle sizes.Regarding sulfate erosion resistance,the mass loss and unconfined compressive strength loss of the RBCA cement-stabilized materials at 56 days were highest for the 19-31.5 mm particle size of the RBA.In terms of compaction and sulfate resistance,it is recommended to use 4.75-19 mm RBA in RBCA cement-stabilized materials.展开更多
To explore mix proportion design of RAC with aggregates tightly packed,the dry and wet packing density of recycled coarse aggregates mixture system and recycled coarse and fine aggregates were tested,then the influenc...To explore mix proportion design of RAC with aggregates tightly packed,the dry and wet packing density of recycled coarse aggregates mixture system and recycled coarse and fine aggregates were tested,then the influence of replacement rate and particle size ratio on the packing density of particle system was explored,the packing density prediction model of recycled coarse aggregates based on particle morphology was constructed,and the mix proportion optimization for recycled aggregate concrete with dry-wet packing model was carried out.The experimental results show that,with the increasing of recycled aggregate replacement rate or fine-grained volume ratio,the dry packing density of recycled coarse aggregates decreases gradually.With the increasing of replacement rate,the particle gradation can be optimized by increasing coarsegrained volume ratio.There is a significant effect for particle morphology parameter K and the particle size ratio on the packing density of the binary mixed system,and the packing density prediction model of recycled coarse aggregates based on particle morphology was constructed.The maximum increase in compressive strength and tensile strength of RAC with mix proportion optimized by the dry-wet packing model are 12.94%and 11.09%,and the cementitious materials is reduced by 21.83%,then the superiority of the mix proportion optimization of RAC with the dry-wet close packing model is confirmed.The results of this paper can provide a theoretical basis for the mix proportion design of RAC.展开更多
In recent years,the amount of waste generated during milling has increased dramatically,and improper disposal poses a significant environmental challenge.To mitigate environmental pollution and enhance the road perfor...In recent years,the amount of waste generated during milling has increased dramatically,and improper disposal poses a significant environmental challenge.To mitigate environmental pollution and enhance the road performance of emulsified asphalt cold recycled mixtures(ECRM),this study employed recycled asphalt pavement(RAP)and reclaimed inorganic binder stabilized aggregate(RAI)as dual recycled materials for ECRM preparation.The blending ratios of reclaimed base and surface layer mixtures significantly influence ECRM's performance,with adjusted proportions substantially improving compressive strength and dynamic modulus.Firstly,three distinct proportioning options were developed for the recycled materials.Mix designs incorporating varying RAP/RAI ratios were used to determine the optimal mix parameters:moisture content,cement dosage,and emulsified asphalt content.Subsequently,comprehensive performance evaluations were conducted through high-temperature wheel tracking tests,freeze-thaw splitting tests,uniaxial compression tests,and dynamic modulus measurements to analyze the pavement characteristics of the three ECRM formulations.Experimental results demonstrate:Compared with ECRM with a blending ratio of RAP:RAI:new aggregate=30:50:20(Option 1),the dynamic stability,freeze-thaw splitting strength ratio,compressive strength,and compressive resilient modulus of ECRM under Option 3(RAP:RAI:new aggregate=50:30:20)decreased by 31.8%,5.2%,16.4%,and 13.1%,respectively.This indicates that increasing RAP content while reducing RAI proportion enhances the tensile strength of ECRM,yet adversely affects its high-temperature stability,moisture resistance,and compressive performance.This work not only addresses the challenge of jointly utilizing asphalt pavement waste and base waste,but also provides a cost-effective and sustainable method for the stable application of milling material resources in road engineering.展开更多
This work examines the environmental and geochemical impact of recycled aggregate concrete production with properties representative for structural applications.The environmental influence of cement content,aggregate ...This work examines the environmental and geochemical impact of recycled aggregate concrete production with properties representative for structural applications.The environmental influence of cement content,aggregate production,transportation,and waste landfilling is analysed by undertaking a life cycle assessment and considering a life cycle inventory largely specific for the region.To obtain a detailed insight into the optimum life cycle parameters,a sensitivity study is carried out in which supplementary cementitious materials,different values of natural-to-recycled aggregate content ratio and case-specific transportation distances were considered.The results show that carbon emissions were between 323 and 332 kgCO_(2)e per cubic metre of cement only natural aggregate concrete.These values can be reduced by up to 17%by replacing 25%of the cement with fly ash.By contrast,carbon emissions can increase when natural coarse aggregates are replaced by recycled aggregates in proportions of 50%and 100%,and transportation is not included in analysis.However,the concrete with 50%recycled aggregate presented lower increase,only 0.3%and 3.4%for normal and high strength concrete,respectively.In some cases,the relative contribution of transportation to the total carbon emissions increased when cement was replaced by fly ash in proportions of 25%,and case-specific transportation distances were considered.In absolute values,the concrete mixes with 100%recycled aggregates and 25%fly ash had lower carbon emissions than concrete with cement and natural aggregates only.Higher environmental benefits can be obtained when the transportation distances of fly ash are relatively short(15–25 km)and the cement replacement by fly ash is equal or higher than 25%,considering that the mechanical properties are adequate for practical application.The observations from this paper show that recycled aggregate concrete with strength characteristics representative for structural members can have lower carbon emissions than conventional concrete,recommending them as an alternative to achieving global sustainability standards in construction.展开更多
The characteristics of surface appearances,mass loss,relative dynamic modulus of elasticity and strength loss of different recycled aggregate concretes(RAC) exposed to freeze-thaw cycles were analyzed.It was found tha...The characteristics of surface appearances,mass loss,relative dynamic modulus of elasticity and strength loss of different recycled aggregate concretes(RAC) exposed to freeze-thaw cycles were analyzed.It was found that the freeze-thaw resistance of RAC could be determined by the recycled aggregate compositions and admixtures.Both the saturation degree and the air void structure were the key factors influencing the freeze-thaw damage on concrete.Some major proposed freeze-thaw deterioration mechanisms were utilized to interpret the freeze-thaw damage on recycled aggregate concrete.Meanwhile,some potential measures to enhance the freeze-thaw resistance of concrete were summarized and discussed.展开更多
The effects of fly ash on the compressive strength, pore size distribution and chloride-ion penetration of recycled aggregate concrete were investigated. Two series of concrete mb：tures were prepared. The concrete mi...The effects of fly ash on the compressive strength, pore size distribution and chloride-ion penetration of recycled aggregate concrete were investigated. Two series of concrete mb：tures were prepared. The concrete mixtures in series I had a water-to-binder ratio and a cement content of 0.55 and 410 kg/ m^3 , respectively. The concrete rnixtures in series II had a water-to-binder ratio and a cement content of 0.45 and 400 kg/ ml respectively. Recycled aggregate was ased as 20% , 50% , and 100% replacements of natural coarse aggregate in the concrete mixtures in both series. In cutdition, fly ash was used as 0% , 25% and 35% by weight replacements of cement. The results show that the compressive strengths of the concrete decreased as the recycled aggregate and the fly ash contents increased. The total porosity and average porosity diameter of the concrete increased us the recycled aggregate content increased. Furtherrruore , an increase in the recycled aggregate content decreased the resistance to chloride ion penetration. Nevertheless, the replacement of cement by 25% fly ush improved the resistance to chloride ion penetration and pore diameters and reduced the total porosity of the recycled aggregate concrete.展开更多
Sixteen controlled low-strength material( CLSM)mixtures with various cement-to-sand( C/Sa) ratios and water-to-solid( W/So) ratios were prepared using recycled fine aggregate from urban red brick based construction wa...Sixteen controlled low-strength material( CLSM)mixtures with various cement-to-sand( C/Sa) ratios and water-to-solid( W/So) ratios were prepared using recycled fine aggregate from urban red brick based construction waste.The fluidity and bleeding of the fresh CLSM mixtures were measured via the modified test methods, and the hardened CLSM mixtures were then molded to evaluate their compressive strength and durability. The results showthat the fluidity of the fresh CLSM mixtures is 105 to 227 mm with the corresponding bleeding rate of 3. 7% to 15. 5%, which increases with the increase in fluidity. After aging for 28 d,the compressive strength of the hardened CLSM mixtures reaches 1. 15 to 13. 96 M Pa, and their strength can be further enhanced with longer curing ages. Additionally, the strength increases with the increase of the C/Sa ratio, and decreases with the increase of the W/So ratio under the same curing age. Based on the obtained compressive strength, a fitting model for accurately predicting the compressive strength of the CLSM mixtures was established, which takes into account the above two independent variables( C/Sa and W/So ratios).M oreover, the durability of the hardened CLSM mixtures is enhanced for samples with higher C/Sa ratios.展开更多
文摘Received:06 December 2025;Accepted:25 February 2026;Published:30 March 2026 ABSTRACT:In the last decade,the importance of sustainable construction and artificial intelligence(AI)in civil engineering has been underlined in many studies.Numerous studies highlighted the superiority of AI techniques over simple and mathematical regression analyses,which suffer from relatively poor generalization and an inability to capture highly non-linear relationships among inputs and output(s)parameters.In this study,to evaluate the compressive strength of concrete with glass powder(GP)and recycled aggregates,600 concrete samples were tested in the laboratory,and their results were evaluated.For intelligent assessment of concrete compressive strength(CCS),the study utilized an improved artificial neural network(ANN)with particle swarm optimization(PSO)algorithm and imperialist competitive algorithm(ICA).For training the models,the experimentally obtained data were used.The concrete ingredients formed the inputs of the AI-based predictive models of CCS.The experimental findings reveal that the implementation of recycled coarse aggregates in concrete from a sustainable construction point of view is advantageous and can enhance the CCS by 11.43%.Apart from that,findings indicate that utilization of 10%GP can lead to a nearly 20%increase in CCS(from 44.6 to 54.1 MPa).Additionally,the experimental observations show almost 40%improvement of CCS when 5%micro silica was used in the concrete mixture.Based on the findings,the study suggests the utilization of waste glass powder to partially replace cement in concrete,which can reduce the amount of cement production.This reduction from economic,energy-saving,and environmental(reduction in greenhouse gas emissions)points of view is of interest.On the other hand,the AI results show that the PSO-based ANN model outperforms the ICA-based ANN for the utilized dataset.According to the findings,the PSO-based ANN predictive model(with a coefficient of determination value of 0.939 and root mean square value of 0.113 for testing data)is a capable tool in predicting the CCS.Hence,this study recommends the implementation of AI-based models in CCS assessment.
基金Funded by the Natural Science Foundation of Jiangsu Province(No.BK20220626)the National Natural Science Foundation of China(No.52078068)+2 种基金Science and Technology Innovation Foundation of NIT(No.KCTD006)Jiangsu Marine Structure Service Performance Improvement Engineering Research CenterKey Laboratory of Jiangsu"Marine Floating Wind Power Technology and Equipment"。
文摘We investigated the effects of fly ash(FA)content on the mechanical properties of recycled aggregate concrete(RAC)and its regeneration potential under freeze and thaw(F-T)cycles.The physical properties of second-generation recycled concrete aggregates(RCA)were used to analyze the regeneration potential of RAC after F-T cycles.Scanning electron microscopy was used to study the interfacial transition zone microstructure of RAC after F-T cycles.Results showed that adding 20%FA to RAC significantly enhanced its mechanical properties and frost resistance.Before the F-T cycles,the compressive strength of RAC with 20%FA reached 48.3 MPa,exceeding research strength target of 40 MPa.A majority of second-generation RCA with FA had been verified to attain class Ⅲ,which enabled their practical application in non-structural projects such as backfill trenches and road pavement.However,the second-generation RCA with 20%FA can achieve class Ⅱ,making it ideal for 40 MPa structural concrete.
基金Funded by"Green Construction and Maintenance of Road Engineering"the Belt and Road Joint Laboratory,International(Hong Kong,Macao and Taiwan)Science and Technology Cooperation Project(No.Z251100007125040)the National Key R&D Program of China(No.2022YFC3803403)+3 种基金the Project of Construction and Support for High-level Innovative Teams of Beijing Municipal Institutions(No.BPHR20220109)the Cultivation Project Funds for Beijing University of Civil Engineering and Architecture(No.X24013)the BUCEA Doctor Graduate Scientific Research Ability Improvement Project(No.DG2024016)the China Scholarship Council(No.202408110091)。
文摘A comprehensive full-sieve-hole grading correction method was used to adjust aggregate gradings.The fatigue properties of recycled concrete aggregate(RCA)asphalt mixtures were investigated using an improved indirect tensile fatigue test under temperature-humidity coupling based on 20-year meteorological data of Beijing,and the degeneration mechanism was further explored by scanning electron microscopy and energy-dispersive spectroscopy.The experimental results indicate that replacing 5-20 mm coarse limestone aggregate(LA)with RCA at a 50% substitution volume can mitigate the impact of RCA variations on the asphalt mixture proportioning design.All RCA asphalt mixtures have lower initial fatigue properties than the LA asphalt mixture.However,under temperature-humidity coupling,the long-term fatigue property of an RCA asphalt mixture with a low proportion of recycled brick exceeds that of the LA asphalt mixture,and the fatigue life decline rate of the RCA asphalt mixture during 10-year service decreases by approximately 25%.This is due to the penetration of the asphalt mortar into the RCA through the pores and cracks on the RCA surface.It forms an interfacial transition zone composed of asphalt mortar and cement mortar and further reduces the mixture damage caused by the water and freeze-thaw conditions.
基金Funded by Natural Science Foundation of Guangxi(No.2025GXNSFBA069565)Guangxi Science and Technology Program(No.AD25069101)Guangxi Bagui Scholars Fund。
文摘Crushing waste coral concrete into recycled aggregates to create recycled coral aggregate concrete(RCAC)contributes to sustainable construction development on offshore islands and reefs.To investigate the impact of recycled coral aggregate on concrete properties,this study performed a comprehensive analysis of the physical properties of recycled coral aggregate and the basic mechanical properties and microstructure of RCAC.The test results indicate that,compared to coral debris,the crushing index of recycled coral aggregate was reduced by 9.4%,while porosity decreased by 33.5%.Furthermore,RCAC retained the early strength characteristics of coral concrete,with compressive strength and flexural strength exhibiting a notable increase as the water-cement ratio decreased.Under identical conditions,the compressive strength and flexural strength of RCAC were 12.7% and 2.5% higher than coral concrete's,respectively,with porosity correspondingly reduced from 3.13% to 5.11%.This enhancement could be attributed to the new mortar filling the recycled coral aggregate.Scanning electron microscopy(SEM)analysis revealed three distinct interface transition zones within RCAC,with the‘new mortar-old mortar’interface identified as the weakest.The above findings provided a reference for the sustainable use of coral concrete in constructing offshore islands.
文摘Egypt has a high attitude in construction and demolition waste (CDW) amounts causing a negative impact on the environment. The use of such waste for infrastructures applications can be useful for each environment and in addition an economic benefit to it in the construction. This study explores the possibility of replacing natural coarse aggregate with recycled concrete construction and demolition waste aggregate for general purpose concrete (i.e. plain concrete and low strength structural concrete). Different samples of CDW were extracted from different demolition sites and landfill locations around Tanta city area for the experimental investigation. CDW was crushed with all its hard constituents (e.g. concrete, brick etc.) found in the landfill. Coarse size crushed CDW was used as a coarse aggregate for concrete. Main characteristics of CDW aggregate determined in addition to the main properties of concrete which was made using this aggregate were measured. The results showed that the CDW could be transformed into recycled concrete aggregate leading to reduction in the concrete compressive strength ranged from 37% to 62% depending on the type of the CDW constituents.
基金Project(2024JJ2073)supported by the Science Fund for Distinguished Young Scholars of Hunan Province,ChinaProjects(2023YFC3807205,2019YFC1904704)+4 种基金supported by the National Key R&D Program of ChinaProject(52178443)supported by the National Natural Science Foundation of ChinaProject(2024ZZTS0109)supported by Fundamental Research Funds for the Central Universities of Central South University,China。
文摘Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.
基金Funded by the Project of National Key Research and Development Program of China(No.2019YFC1906202)。
文摘In order to study the effects of the contents of used mortar recycled aggregate(OMRA)and brick recycled aggregate(BRA)on the deformation properties of recycled aggregate concrete(RAC),under uniaxial compression conditions,The RAC of OMRA(0%,5%,10%,and 15%)and BRA(0%,3%,6%,9%,12%,and 15%)were studied.The experimental results show that,under uniaxial compression,the interfacial relationships of RAC containing OMRA and BRA between different materials are more complex,and the failure mechanism is also more complex.The content of OMRA and BRA had significant influence on the deformation behavior of RAC.When the content of OMRA and BRA is high,it is difficult for existing formulas and models to accurately represent the actual value.In this study,the influence of OMRA and BRA content is taken into account,and the existing formulas for calculating concrete deformation are modified,so that these formulas can more accurately calculate the elastic modulus,peak strain and ultimate strain of recycled concrete.The stress-strain formula of Guo concrete fits the stress-strain curve of concrete very well.We modified the formula on the basis of Guo formula to make the formula more suitable for the stress-strain curve of recycled concrete containing old mortar and brick,and the theoretical model proposed has better fitting accuracy.The study provides a valuable reference for nonlinear analysis of recycled aggregate concrete structures under different proportions of OMRA and BRA.
文摘Exploring alternative aggregates or recycled aggregates to substitute traditional concrete aggregates,particularly sand aggregates,which are becoming more limited and must comply with environmental protection standards,is essential.Research has explored various alternative materials to sand in concrete,including concrete from demolished buildings,and broken glass from projects,among others.Investigating the use of recycled broken glass to substitute sand aggregates and implementing this research in compression columns is crucial.This paper examines the compressive behavior of reinforced concrete columns that utilize recycled glass particles as a substitute for sand in concrete.The research findings establish the relationships:load and vertical displacement,load and deformation at the column head,mid-column,and column base;the formation and propagation of cracks in the column,while considering factors such as the percentage of recycled glass,the arrangement of stirrups,and the amount of load-bearing steel influencing the performance of square reinforced concrete columns under compression.The feasibility of using recycled glass as a substitute for sand in column structures subjected to compression has been demonstrated,with the ideal replacement content for sand aggregate in reinforced concrete columns in this study ranging from 0%to 10%.The column’s load-bearing ability dropped from 250 kN to 150 kN when 100%recycled glass was used instead of sand.This is a 40%drop,and cracks started to show up sooner.The research will support recycling broken glass instead of using sand in building,improving the environment and reducing natural sand use.
基金Funded by the Jiangsu Province Industry University Research Project(No.BY20231142)the Yangzhou Science&Technology Program(No.YZ2023061)the Zhenjiang Science&Technology Program(No.SH2022018)。
文摘In order to realize the resource utilization of construction waste,industrial waste slag and silt,this paper used Portland cement,mineral waste residue and phosphogypsum composite to make cementing material(CMPS)with construction waste recycled aggregate to solidify silt.The mechanical properties of the solidified silt were analyzed by laboratory solidification test and microscopic examination respectively.In order to clarify the mineral composition,microscopic morphology and pore characteristics of the regenerated aggregate and CMPS solidified silt,X-ray diffractometer(XRD),scanning electron microscope(SEM),and nitrogen adsorption pore analyzer(NA)were used to further explore and analyze the regenerated aggregate and CMPS solidified silt effectively,and further reveal the internal mechanism of the regenerated aggregate and CMPS solidified silt effectively.The experimental results show that the strength of Portland cement-mineral waste residue phosphogypsum terpolymer system curing agent increases by 107.34%than that of single Port-land cement solidified silt at 56 d,and the strength of CMPS solidified silt increases by 25.68%under the action of recycled aggregate framework.The curing age and moisture content of the silt have a high correlation with the strength of the solidified silt.Therefore,the influence law of the above two influencing factors on its mechanical properties is further explored and the strength prediction is made.The microscopic test results show that,based on the hydration of Port-land cement and the pozzolans reaction of mineral waste residue,the solidified system has produced calcium silicate hydrate gel and ettringite crystals with gelatinous properties,which helps to fill the pores and form a denser structure.
基金supported by the Ongoing Research Funding Program(Grant No.ORFT-2025-025-6)at King Saud University,Riyadh,Saudi Arabia.
文摘Accurately predicting the compressive strength of recycled aggregate concrete(RAC)incorporating supplementary cementitious materials(SCMs)remains a critical challenge due to the heterogeneous nature of recycled aggregates(RA)and the complex interactions among multiple binder constituents.This study advances the field by developing the most extensive and rigorously preprocessed database to date,which comprises 1243 RAC mixtures containing silica fume,fly ash,and ground-granulated blast-furnace slag.A hybrid,domain-informed machine-learning framework was then proposed,coupling optimized Extreme Gradient Boosting(XGBost)with civil engineering expertise to capture the complex chemical and microstructural mechanisms that govern RAC performance.Systematic grid-search optimization(n_estimators=50,learning_rate=0.2,max_depth=7)produced superior predictive accuracy(training R^(2)=0.9923,testing R^(2)=0.937;MAE=2.378 MPa;RMSE=3.591 MPa),which outperformed Extra Trees,Light Gradient Boosting,and traditional regressors.Beyond prediction,model interpretability was achieved using Shapley additive explanations and partial dependence analyses,which revealed curing age as the dominant strength driver,while water-to-binder ratio and recycled aggregate water absorption exhibited strong negative influences.Three-dimensional interaction plots further demonstrated how optimal superplasticizer dosages reduce the strength loss associated with high recycled aggregate content.In summary,this work provides a novel,explainable,and data-driven framework that achieves high predictive accuracy with mechanistic transparency and offers a powerful,interpretable tool for the design and optimization of sustainable RAC mixtures.
基金Funded by the Natural Science Foundation of Shaanxi Province(No.2023-JC-QN-0553)。
文摘To examine the influences of waste polypropylene fiber(PPF)on the strength and internal pore structure of recycled aggregate concrete incorporating iron ore tailings,both the cubic compressive strength and axial compressive strength of the concrete were measured.Additionally,the microstructure was analyzed using scanning electron microscopy.The evolution of pore structure parameters,including pore size distribution,pore type distribution,and nuclear magnetic resonance spectral area in the concrete,was investigated through nuclear magnetic resonance(NMR)analysis.A model correlating the concrete's pore structure with its macroscopic performance was subsequently developed based on fractal theory.The results demonstrate that an appropriate amount of PPF created a bridging effect that decelerated the progression of macro cracks,enhanced the ductility of the concrete's failure mode,and increased both cubic compressive strength and axial compressive strength,with the most effective dosage being approximately 0.6%.An appropriate amount of PPF(ranging from 0.3%to 0.6%)facilitated the formation of harmless pores and shifted the pore size distribution towards medium and small sizes.Specifically,a fiber content of 0.6%resulted in the most significant reduction in the T2 spectral area.Furthermore,the pore structure of concrete exhibits distinct fractal characteristics.As the PPF content increased,the fractal dimension initially rose and then declined,demonstrating a strong correlation with the mechanical properties.
基金Funded by the National Natural Science Foundation of China(No.52478281)the Natural Science Foundation of Zhejiang Province(No.LZ22E080003)the Science and Technology Project of Zhejiang Provincial Department of Transport(No.202225)。
文摘The degradation performance of pervious concrete containing TiO_(2)/LDHs-loaded recycled aggregates for NO gas was analyzed using a gas phase catalytic degradation test device,simulating different environmental conditions such as load,ambient temperature,and illumination intensity,which provides theoretical support for practical engineering.The experimental results indicate that when the ambient temperature is controlled at 25℃and the illumination intensity is 30 W/m^(2),the sample prepared by soaking recycled aggregates in a 0.8%TiO_(2)/LDHs suspension exhibits the highest photocatalytic degradation rate for NO gas,reaching 72.54%.Further investigation on the influence of environmental temperature reveals that,at 25℃,the maximum photocatalytic degradation rate for NO gas is 72.9%.Moreover,at an illumination intensity of 40 W/m^(2),the maximum photocatalytic degradation rate for NO gas is 87.08%.Additionally,after three repeated photocatalytic tests,the sample demonstrates good stability,with a photocatalytic degradation rate of 58%.The nitrogen content in the eluent obtained from soaking the sample was determined to be 0.0022 mol/L,with a recovery rate of 80%.The adsorption experiment demonstrates that the sample exhibits a favorable adsorption effect on nitrate ions,reaching a maximum of 56.8%.
基金Funded by the Natural Science Foundation of Jiangsu Province(No.BK20220626)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX24_3174)Taizhou Science and Technology Support Programme(Social Development)Directive Project(No.TS202432)。
文摘The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully replace natural fine aggregates was investigated.The results indicated that a 50% FA content significantly increased the compressive strength of RFA-HDCC by 13.93%.However,a?further increase in FA content led to a drastic decrease.The increased fly ash content substantially reduced the flexural and tensile strength;however,it markedly increased the matrix strain capacity,resulting in a 53.73% increase in the peak strain when FA was raised to 70%.Regarding durability,the increase in FA content negatively affected the chloride ion permeability and carbonation resistance.However,the increase in FA content initially improved the frost resistance of RFA-HDCC,peaking at 50% FA and deteriorating at 60% and 70% FA content.
基金Funded by the National Natural Science Foundation of China (No.52078068)the Natural Science Foundation of Jiangsu Province (No.BK20220626)。
文摘This study meticulously examined the compaction and sulfate erosion resistance of cement-stabilized materials incorporating recycled brick-concrete aggregate (RBCA).To explore the effects of recycled brick aggregate (RBA) with varying particle sizes,three size ranges (4.75-9.5 mm,9.5-19 mm and 19-31.5 mm) were used to replace 20% of the corresponding particle sizes of recycled concrete aggregate (RCA) in cement-stabilized materials.The findings indicated that cement-stabilized materials utilizing RBA and RCA exhibited a lower maximum dry density and a higher optimum moisture content than natural aggregate cement-stabilized materials.The use of RBA with a particle size of 4.75-9.5 mm resulted in a lower maximum dry density and a higher optimum moisture content than 9.5-19 mm and 19-31.5 mm.Furthermore,the 7-day unconfined compressive strength of RBCA cement-stabilized materials with RBA of 4.75-9.5 mm demonstrated superior results compared to those with larger particle sizes.Regarding sulfate erosion resistance,the mass loss and unconfined compressive strength loss of the RBCA cement-stabilized materials at 56 days were highest for the 19-31.5 mm particle size of the RBA.In terms of compaction and sulfate resistance,it is recommended to use 4.75-19 mm RBA in RBCA cement-stabilized materials.
基金Funded by joint Funds of the National Natural Science Foundation of China(No.U1904188)the Key Research Project of Henan Province for Colleges and Universities(No.26A560009)+3 种基金the Jiaozuo City Science and Technology Planning Project(No.2025210099)the Henan Provincial Science and Technology Research Project(No.252102320305)the Natural Science Foundation of Henan Province(No.252300421917)the Project by Key Laboratory of Intelligent Construction and Safety Operation and Maintenance of Underground Engineering in Henan Province(No.KFKT2024-01)。
文摘To explore mix proportion design of RAC with aggregates tightly packed,the dry and wet packing density of recycled coarse aggregates mixture system and recycled coarse and fine aggregates were tested,then the influence of replacement rate and particle size ratio on the packing density of particle system was explored,the packing density prediction model of recycled coarse aggregates based on particle morphology was constructed,and the mix proportion optimization for recycled aggregate concrete with dry-wet packing model was carried out.The experimental results show that,with the increasing of recycled aggregate replacement rate or fine-grained volume ratio,the dry packing density of recycled coarse aggregates decreases gradually.With the increasing of replacement rate,the particle gradation can be optimized by increasing coarsegrained volume ratio.There is a significant effect for particle morphology parameter K and the particle size ratio on the packing density of the binary mixed system,and the packing density prediction model of recycled coarse aggregates based on particle morphology was constructed.The maximum increase in compressive strength and tensile strength of RAC with mix proportion optimized by the dry-wet packing model are 12.94%and 11.09%,and the cementitious materials is reduced by 21.83%,then the superiority of the mix proportion optimization of RAC with the dry-wet close packing model is confirmed.The results of this paper can provide a theoretical basis for the mix proportion design of RAC.
基金sponsored by National Natural Science Foundation of China(No.52308466)SASAC Science and Technology Innovation Project(JF-23-01-0063)Shaanxi Provincial Transportation Research Project(25-84 K,25-85 K).
文摘In recent years,the amount of waste generated during milling has increased dramatically,and improper disposal poses a significant environmental challenge.To mitigate environmental pollution and enhance the road performance of emulsified asphalt cold recycled mixtures(ECRM),this study employed recycled asphalt pavement(RAP)and reclaimed inorganic binder stabilized aggregate(RAI)as dual recycled materials for ECRM preparation.The blending ratios of reclaimed base and surface layer mixtures significantly influence ECRM's performance,with adjusted proportions substantially improving compressive strength and dynamic modulus.Firstly,three distinct proportioning options were developed for the recycled materials.Mix designs incorporating varying RAP/RAI ratios were used to determine the optimal mix parameters:moisture content,cement dosage,and emulsified asphalt content.Subsequently,comprehensive performance evaluations were conducted through high-temperature wheel tracking tests,freeze-thaw splitting tests,uniaxial compression tests,and dynamic modulus measurements to analyze the pavement characteristics of the three ECRM formulations.Experimental results demonstrate:Compared with ECRM with a blending ratio of RAP:RAI:new aggregate=30:50:20(Option 1),the dynamic stability,freeze-thaw splitting strength ratio,compressive strength,and compressive resilient modulus of ECRM under Option 3(RAP:RAI:new aggregate=50:30:20)decreased by 31.8%,5.2%,16.4%,and 13.1%,respectively.This indicates that increasing RAP content while reducing RAI proportion enhances the tensile strength of ECRM,yet adversely affects its high-temperature stability,moisture resistance,and compressive performance.This work not only addresses the challenge of jointly utilizing asphalt pavement waste and base waste,but also provides a cost-effective and sustainable method for the stable application of milling material resources in road engineering.
文摘This work examines the environmental and geochemical impact of recycled aggregate concrete production with properties representative for structural applications.The environmental influence of cement content,aggregate production,transportation,and waste landfilling is analysed by undertaking a life cycle assessment and considering a life cycle inventory largely specific for the region.To obtain a detailed insight into the optimum life cycle parameters,a sensitivity study is carried out in which supplementary cementitious materials,different values of natural-to-recycled aggregate content ratio and case-specific transportation distances were considered.The results show that carbon emissions were between 323 and 332 kgCO_(2)e per cubic metre of cement only natural aggregate concrete.These values can be reduced by up to 17%by replacing 25%of the cement with fly ash.By contrast,carbon emissions can increase when natural coarse aggregates are replaced by recycled aggregates in proportions of 50%and 100%,and transportation is not included in analysis.However,the concrete with 50%recycled aggregate presented lower increase,only 0.3%and 3.4%for normal and high strength concrete,respectively.In some cases,the relative contribution of transportation to the total carbon emissions increased when cement was replaced by fly ash in proportions of 25%,and case-specific transportation distances were considered.In absolute values,the concrete mixes with 100%recycled aggregates and 25%fly ash had lower carbon emissions than concrete with cement and natural aggregates only.Higher environmental benefits can be obtained when the transportation distances of fly ash are relatively short(15–25 km)and the cement replacement by fly ash is equal or higher than 25%,considering that the mechanical properties are adequate for practical application.The observations from this paper show that recycled aggregate concrete with strength characteristics representative for structural members can have lower carbon emissions than conventional concrete,recommending them as an alternative to achieving global sustainability standards in construction.
基金Funded by the National Key Research and Development Program of China during the“13th Five-Year Plan”(No.2018 YFD1101001)。
文摘The characteristics of surface appearances,mass loss,relative dynamic modulus of elasticity and strength loss of different recycled aggregate concretes(RAC) exposed to freeze-thaw cycles were analyzed.It was found that the freeze-thaw resistance of RAC could be determined by the recycled aggregate compositions and admixtures.Both the saturation degree and the air void structure were the key factors influencing the freeze-thaw damage on concrete.Some major proposed freeze-thaw deterioration mechanisms were utilized to interpret the freeze-thaw damage on recycled aggregate concrete.Meanwhile,some potential measures to enhance the freeze-thaw resistance of concrete were summarized and discussed.
基金Funded by the Environment and Conservation Fund, the WooWheelock Green Fund andthe Hong Kong Polytechnic University
文摘The effects of fly ash on the compressive strength, pore size distribution and chloride-ion penetration of recycled aggregate concrete were investigated. Two series of concrete mb：tures were prepared. The concrete mixtures in series I had a water-to-binder ratio and a cement content of 0.55 and 410 kg/ m^3 , respectively. The concrete rnixtures in series II had a water-to-binder ratio and a cement content of 0.45 and 400 kg/ ml respectively. Recycled aggregate was ased as 20% , 50% , and 100% replacements of natural coarse aggregate in the concrete mixtures in both series. In cutdition, fly ash was used as 0% , 25% and 35% by weight replacements of cement. The results show that the compressive strengths of the concrete decreased as the recycled aggregate and the fly ash contents increased. The total porosity and average porosity diameter of the concrete increased us the recycled aggregate content increased. Furtherrruore , an increase in the recycled aggregate content decreased the resistance to chloride ion penetration. Nevertheless, the replacement of cement by 25% fly ush improved the resistance to chloride ion penetration and pore diameters and reduced the total porosity of the recycled aggregate concrete.
基金The National Science and Technology Support Program of China(No.2014BAC07B03)the Science and Technology Project of Transportation Committee of Beijing Government(No.2016-LZJKJ-01-006)the National Natural Science Foundation of China(No.51278016)
文摘Sixteen controlled low-strength material( CLSM)mixtures with various cement-to-sand( C/Sa) ratios and water-to-solid( W/So) ratios were prepared using recycled fine aggregate from urban red brick based construction waste.The fluidity and bleeding of the fresh CLSM mixtures were measured via the modified test methods, and the hardened CLSM mixtures were then molded to evaluate their compressive strength and durability. The results showthat the fluidity of the fresh CLSM mixtures is 105 to 227 mm with the corresponding bleeding rate of 3. 7% to 15. 5%, which increases with the increase in fluidity. After aging for 28 d,the compressive strength of the hardened CLSM mixtures reaches 1. 15 to 13. 96 M Pa, and their strength can be further enhanced with longer curing ages. Additionally, the strength increases with the increase of the C/Sa ratio, and decreases with the increase of the W/So ratio under the same curing age. Based on the obtained compressive strength, a fitting model for accurately predicting the compressive strength of the CLSM mixtures was established, which takes into account the above two independent variables( C/Sa and W/So ratios).M oreover, the durability of the hardened CLSM mixtures is enhanced for samples with higher C/Sa ratios.
